Development of a tunable, narrow linewidth 2.066 micrometer holmium, thulium: yttrium lithium fluoride laser for open-path remote sensing of atmospheric carbon dioxide and water vapor

A tunable, narrow-frequency, continuous wave 2.066 {dollar}mu{dollar}m Ho:YLF laser was developed, characterized, and used for the first time in preliminary spectroscopic measurements of CO{dollar}sb2{dollar} and water vapor in the laboratory and atmosphere. The laser was constructed using a 4 mm long, codoped 5% Tm and 0.5% Ho Yttrium Lithium Fluoride (YLF) crystal that was cut at Brewster's angle, cooled to -15{dollar}spcirc{dollar}C using a TE cooler, and pumped by an Ar{dollar}sp+{dollar} pumped Ti:Sapphire laser operating at 792 nm. Intracavity etalons were used to reduce the laser linewidth to about 0.025 cm{dollar}sp{lcub}-1{rcub}{dollar}, consisting of two longitudinal modes. The peak Ho:YLF laser output power with intracavity etalons was about 32 mW at a pump power of 500 mW. The laser wavelength was continuously tunable across the laser cavity longitudinal modes over about a 6 cm{dollar}sp{lcub}-1{rcub}{dollar} range. The output beam profile was nearly Gaussian, but had a slight astigmatism and possibly some higher order transverse modes.; The Ho:YLF laser was used to perform spectroscopic measurements on molecular CO{dollar}sb2{dollar} in a laboratory absorption cell. The transmission spectra of CO{dollar}sb2{dollar} were taken across several absorption lines of CO{dollar}sb2{dollar} and the measured peak transmission and linewidth agreed within {dollar}pm{dollar}8 and {dollar}pm{dollar}5% respectively, with those published previously. The discrepancies were attributed to the asymmetric multimode operation of the laser.; The Ho:YLF laser was also used to measure the concentration of CO{dollar}sb2{dollar} and of water vapor in the atmosphere. Preliminary path averaged concentration measurements of CO{dollar}sb2{dollar} were taken for a 135 m path over a parking lot. The CO{dollar}sb2{dollar} concentration was found to be about 450 to 550 ppm ({dollar}pm{dollar}20%) which is somewhat higher than the accepted world average concentration of CO{dollar}sb2{dollar} of 330 ppm. In addition, the measured water vapor concentration over the same path was found to be about 2000 ppm ({dollar}pm{dollar}20%) which was within about 15% of the actual value.